This invention concerns improvements in or relating to emergency lighting, especially emergency lighting used to indicate an escape path leading to an exit for evacuation of a passenger vehicle in an emergency, for example following an accident.
The invention has particular application to passenger vehicles of the type in which rows of seats are provided on either side of an aisle with an exit at one or both ends of the aisle and/or on one or both sides of the aisle between the ends. Examples of this type of passenger vehicle include aircraft, trains and coaches.
Vehicles of this type are designed to carry a large number of passengers in a confined space. For example, each row may seat two or three passengers on each side of the aisle which is normally only wide enough for one passenger to move along between the aisle seats.
As a result, there may be several passengers in each row who have to access the aisle one at a time and move along the aisle to an exit. Furthermore, as passengers move along the aisle, they obstruct and restrict access to the aisle of other passengers in the rows. It will be understood therefore that passengers must keep moving along the aisle towards the exit(s) to evacuate the vehicle in an efficient, orderly manner. Accordingly, there is a need to ensure that passengers can find their way to the exit(s) easily and reliably.
In most vehicles of this type, an electrical lighting system is fitted at ceiling level which provides sufficient lighting for passengers to evacuate the vehicle under normal circumstances. However, in an emergency following an accident, the electrical lighting system may be inoperable if the electrical connections to the power source are damaged. For example, the electrical connections may be broken by impact damage to the structure of the vehicle or by outbreak of a fire following a crash. Moreover, even if the lighting system remains operable, the outbreak of fire may render the lighting system ineffective if the light is blocked by smoke filling the interior of the vehicle.
The lighting system may also fail in other circumstances without an accident due to faults arising in normal service making it difficult for passengers to leave the vehicle safely at night or in conditions of low ambient light.
For these reasons, it is desirable, and in the case of aircraft mandatory, to provide an emergency lighting system as a back-up to the normal lighting system. Typically, such emergency lighting is provided at floor level and identifies the path leading to the exit(s) for passengers to follow. In this way, if the interior of the vehicle fills with smoke, the emergency lighting is below the smoke level allowing passengers to crawl to the exit(s) along the path illuminated by the emergency lighting.
Traditionally, such emergency lighting has been electrical with the wiring and power source separate from that of the lighting system provided at ceiling level for normal use. The provision of a separate emergency lighting system adds considerably to the costs for initial installation and subsequent maintenance in service with regular checks to ensure operability. In the case of aircraft, the system must be checked each time before take-off and the aircraft is grounded if any repairs are required. The resulting delay is inconvenient for passengers and adds to the running cost for the aircraft operator, especially if a take-off slot has to be vacated.
A further problem of such electrical emergency lighting systems is the extra weight of the storage batteries normally employed as the separate power source which adds to operating costs. Thus, fuel costs may be increased and/or, in the case of aircraft, the number of passengers may have to be reduced to compensate for the extra weight.
The most important disadvantage of the known electrical emergency lighting systems however, is probably that they suffer from the same problem of the electrical connections being broken in a crash resulting from structural damage to the vehicle and/or from fire. Accordingly, such emergency lighting systems can be rendered inoperative just at the very time they are required to assist passengers to evacuate the vehicle.
It is desirable therefore to provide an emergency lighting system which does not depend on electrical connections to a power source to provide the required level of illumination. One such system for use in an aircraft is described in our UK Patent No. 2 314 536 in which the path to the exit(s) is illuminated by photoluminescent material incorporated into a track extending along the aisle for passengers to follow to the exit(s). The photoluminescent material is chosen to provide an acceptable level of illumination over a period of time sufficient for the passengers to evacuate the aircraft.
The emergency lighting system described in our afore-mentioned patent has met with considerable success due to the many benefits and advantages for both the manufacturer and operator of aircraft in which the system is fitted. Thus, the system does not require connection to a power source thereby eliminating completely the wiring and separate storage batteries required for conventional electrical emergency lighting systems.
In one arrangement, the track comprises an outer housing and an insert provided with the photoluminescent material received within the outer housing. The outer housing includes a base and a separate cover which are releasably connected together to locate and retain the insert. The base and cover are made of plastics such as polycarbonate with at least the cover being transparent or translucent to allow the light emitted by the photoluminescent material to pass through.
By forming the track in this way, when a cover is worn or damaged in service, a replacement cover can be fitted to the existing base and insert allowing the track to be repaired with minimum delay and disruption. In this way, cost savings can be made for maintenance of the track. There can be occasions, however, when it is more convenient to replace the entire track, for example during refurbishment of an aircraft, and in these circumstances the insert may be recovered and re-used. This may allow further cost savings to be made.